This invention relates to a circuit arrangement comprising a first amplifier circuit which includes two cross-coupled differential amplifiers each of which comprises two transistors having a common emitter branch to which input signals are applied. One transistor of each differential amplifier is connected to the output of the amplifier circuit via its collector.
A circuit with two cross-coupled differential amplifiers comprises four transistors, each of which has one electrode (emitter, collector or base) connected in common with a corresponding electrode of only one transistor of the three other transistors. In particular such cross-coupled differential amplifiers are used on a large scale in integrated circuit technology. However, it is known that they may give rise to non-linear distortion, which in some cases becomes impermissible.
It is known that non-linear distortion may be reduced by negative feedback.
In a volume or a tone-control circuit comprising two cross-coupled differential amplifiers, as is known from U.S. Pat. No. 3,908,172, the negative feedback depends on the desired volume or the desired frequency response respectively. The negative feedback may become so small over a part of the adjustment range that the non-linear distortion can no longer be eliminated to a satisfactory extent.
It is furthermore known that the emitter-path resistances of the transistors of the cross-coupled differential amplifiers cause said distortion and that the non-linearities can be minimized if the emitter-path resistances are minimized (DE-OS 24 18 455). However, when use is made of integrated circuit technology this solution demands a substantial surface area.